<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>03JS数据类型</title>
</head>
<body>
    <script>
        //JS数据类型=原始类型+引用类型
        //原始类型：number string boolean null undefined
        var a = 1;
        var b = 9.9;
        console.log(a,typeof a,typeof b)
        var c = '你好';
        var d = '你好';
        console.log(c,typeof c,d,typeof d)
        var e = true;
        var f = false;
        console.log(e,typeof e,f,typeof f)
        //声明了变量但未赋值，会得到undefined，未定义型
        var g;
        console.log(g,typeof g);

        //引用类型：object Number String Boolean Array Function Date RegExp
        //1.自定义JS对象
        let obj = {
            name:'张三',
            age:18
        }
        console.log(obj,typeof obj)
        console.log(obj.name,obj.age)

        obj.age=19;
        console.log(obj);//{name:'张三'，age：19}

        //给对象动态新增一个like属性
        obj.like = '吃火锅';
        console.log(obj);//{name：‘张三’，age：19，like：‘吃火锅’}
        console.log(obj.like);//吃火锅
        console.log(obj.play);//undefined,访问对象不存在的属性会得到undefined

        //JS数组
        let arr = ['张三','李四','王五',1,2,3,4,false];
        console.log(arr,typeof arr);
        console.log(arr[0]);
        console.log(arr[5]);
        console.log(arr[99]);//访问数组不存在的下标，会得到undefined

    </script>

</body>
</html>